Spectroscopic (FT-IR/FT-Raman) and computational (HF/DFT) investigation and HOMO/LUMO/MEP analysis on 1,1-difluoro-2-vinyl- cyclopropane P. Senthil Raj a,⇑ , D. Shoba b , S. Ramalingam c , S. Periandy d a PRIST University, Vallam, Thanjavur, India b Periyar Maniammai University, Thanjavur, India c Department of Physics, A.V.C. College, Mayiladuthurai, Tamilnadu, India d Department of Physics, Tagore Arts College, Puducherry, India highlights  FT-IR/FT-Raman spectra of 1,1- difluoro-2-vinyl-cyclopropane were recorded.  The chemical shift was found and it is favor for its change of chemical property.  The vibrational properties of the molecule have been studied.  The electronic properties were studied using frontier molecular orbital analysis.  The thermodynamical parameters have been studied for different temperature. graphical abstract 1,1-Difluoro-2-vinyl-cyclopropane is used an intermediates in the synthesis of complex molecules because of their ready reactivity. Cyclopropane analogues are proved to show varied biological applica- tions such as anti-HIV, anticancer, antibacterial, antifungal, antiviral, antitumor, COX-II inhibitor proper- ties. Due to their diverse applications in synthetic, agricultural, and medicinal chemistry as well as in material science a thorough analysis of the physical and chemical properties of 1,1-difluoro-2-vinyl- cyclopropane is made. article info Article history: Received 14 June 2014 Received in revised form 7 March 2015 Accepted 10 March 2015 Available online 31 March 2015 Keywords: 1,1-Difluoro-2-vinyl-cyclopropane GIAO Chemical shifts Frontier molecular orbitals and molecular electrostatic potential abstract All the computational calculations were made in the ground state using the HF and DFT (B3LYP) methods with 6-31++G (d,p) and 6-311++G (d,p) basis sets. Making use of the recorded data, the complete vibra- tional assignments were made and analysis of the observed fundamental bands of molecule was carried out. The shifting of the frequencies in the vibrational pattern of the title molecule due to the sub- stitutions; ACH@CH 2 and F were deeply investigated by the vibrational analysis. Moreover, 13 C NMR and 1 H NMR chemical shifts were calculated by using the gauge independent atomic orbital (GIAO) method with HF/B3LYP methods with 6-311++G (d,p). A study on the electronic properties, such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. Mulliken charges of the 1DF2VCP were also calculated and interpreted. The thermodynamic properties (heat capacity, entropy, and enthalpy) of the title compound at different temperatures were calculated in gas phase. Ó 2015 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.saa.2015.03.084 1386-1425/Ó 2015 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +91 9843425541. E-mail address: senstarphy@gmail.com (P. Senthil Raj). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 147 (2015) 293–302 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa